


conductor caught in slow motion

by kathillards



Category: Kamen Rider Build
Genre: M/M, Sound/Touch Synesthesia, Unresolved Sexual Tension, Voice Kink, it gets resolved don't worry
Language: English
Status: Completed
Published: 2018-02-12
Updated: 2018-02-12
Packaged: 2019-03-17 06:36:08
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,364
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13653477
Author URL: https://archiveofourown.org/users/kathillards/pseuds/kathillards
Summary: His voice is right next to Sento’s ear, and it feels like feathers sliding over his bare skin, around his neck and under his shirt. Sento sucks in a breath through his teeth and doesn’t reply.(or, Sento has sound/touch synesthesia and it's mostly fine until he hears Ryuga's voice.)





	conductor caught in slow motion

Because of the amnesia, it’s impossible to tell when this started, but Sento notices it first with Misora when she’s putting on her internet idol persona.

Before then, it hadn’t been anything unusual—Sento knows how wires get crossed in your brain and it wasn’t too weird when the owner’s shoes on the floor made him feel like someone is writing on his hands, or that Misora talking to him feels warm like being near a fire.

It’s when she changes her voice and the squeal of Mii-tan makes his skin prickle like he’s stepped into a spider web that he realizes this might be a problem. If enough sounds overwhelm him, it could be a catastrophe on the battlefield.

He learns tricks to muffle it, mute the effects certain sounds have on his body. He forces himself to listen to nails on a chalkboard for days on end until he’s so used to it that it no longer feels like someone has scratched a rusty fork over his arms. For some reason, the sounds of a fight—shouting, punching, kicking—don’t have nearly as much of an effect as normal, everyday sounds.

The theory goes that too much stimuli of his other senses stifles the effect of the synesthesia with sounds. Not that he tells people about this—some things, Misora doesn’t need to know to hold over him.

In hindsight, he should’ve known the problem would be not a battlefield, but a person.

.

Ryuga Banjou is loud, first of all. He’s angry and bursting with emotion and always ready to use his fists to speak for him. When Sento rescues him, he hadn’t noticed, too distracted with understanding the truth of what happened, and the ethics of saving him, and fighting, and escaping.

It’s when they’re riding back to the café, finally having lost the guards that were chasing them, and Ryuga has finally settled down and relaxed a little, that he says, right from behind Sento, “Where are you taking me anyway?”

Ryuga isn’t touching him, not really, his hands on the seat of the bike, his body a respectable distance from Sento’s despite both of them sharing one seat. So it makes no sense why, all at once, it feels like someone has traced a finger down his spine and around his collarbone and on the back of his knees, lingering and secretive.

Sento barely stops his shiver in time. “A café,” he says carefully, each word seeming to take a great deal more effort to say than it should. “You’ll be safe there.”

“You don’t have a house?” Ryuga asks skeptically.

His voice is right next to Sento’s ear, and it feels like feathers sliding over his bare skin, around his neck and under his shirt. Sento sucks in a breath through his teeth and doesn’t reply. It’ll be better once they get home and Misora’s voice can put him back to normal, he tells himself. There’s no way this will last.

.

But every time Ryuga starts yelling, instead of snapping to anger, or condescension like he would _like_ to, the first thing Sento feels is always the sensation of white-hot hands pressing into his chest, down his back, stroking up his arms. It’s intoxicating and exhausting all at once; he keeps himself awake at night just imagining his voice and the touches that go along with it.

At a certain point, it starts to be embarrassing.

“What’s the matter with you?” Misora asks once when he’s sulking out in the café to avoid Ryuga. She has that tone of voice like she’s supremely unimpressed with whatever he’s about to say, and that, at least, makes him feel normal, just a calming breeze passing over him.

“I don’t like…” Sento trails off, chewing on his lips. Even the memory of Ryuga’s voice is hard to think about, makes him feel like there are hands kneading his back till he’s melting. “I don’t like his voice,” he confides in her.

Misora cocks her head. “Because… it’s annoying?”

“…Yeah,” he lies. “Because he’s annoying.”

.

In his defense, Ryuga _is_ annoying. He gets in Sento’s business, he demands answers when Sento’s not even sure of the right questions to ask, he doesn’t have his priorities straight and only cares about himself.

And he won’t shut up. He _doesn’t_ shut up. Even while Sento is trying to work on his projects, unearth the truth, get research done in the lab, he’s always around, wandering in circles around their tiny laboratory and babbling away about god knows what. Sento’s mastered the art of tuning out his words, but his voice is a whole other story.

“Can you shut up, please?” he demands once—actually, he demands it about twice a day, but this time it’s late in the evening and he’s just put down another Smash a few hours earlier and he’s too _tired_ to deal with the way Ryuga’s voice sends goosebumps all along his arms and phantom fingers tracing patterns over his back.

“…Fine,” says Ryuga, looking supremely offended, although Sento doesn’t know what gives him the right, since _he’s_ not the one being slowly tormented by the sound of his voice. “I’m gonna go get some food from the café.”

He walks out in a huff. Sento watches him go, eyes tracking him the whole way up the stairs just to be sure he’s really, truly gone—

And then he lets his shoulders slump, his spine unstiffen, and in the emptiness of the room, the memory of Ryuga’s voice is suddenly the loudest thing in there.

.

He takes great care to keep it a secret, the ghost touches and the aching sensations and the long nights with just his hands and the imprint of Ryuga’s voice to keep him company, because there is nothing that could be worse than telling Ryuga what he does to him, he’s pretty sure.

But sometimes—like when Ryuga looks at him with that thoughtful, surprised look on his face, like Sento isn’t the person he thought he was, or when he saves him from certain death and smiles when Sento makes fun of him—he comes close to letting it slip. Secrets are only dangerous in the wrong hands, after all.

The first time he kisses him, it’s purely to shut him up. He’s yelling at Sento about something—something to do with Touto and Hokuto and proving his innocence—but he can’t concentrate on what Ryuga is saying when it feels like there are red-hot threads snaking all the way around his waist, his hips, his chest, turning every inch of his skin to electricity.

“What—” Ryuga splutters into the kiss until Sento presses their lips together more forcefully just to be sure he can’t say anything. He goes silent after some floundering and then kisses him back, as intensely as if this was an extension of their debates.

“Look,” says Sento quickly when the kiss breaks apart, before Ryuga can say or do anything except stare at him with his eyes rapidly blinking. “I _am_ going to prove your innocence. Just shut up for once and let me think, okay?”

“I—” Ryuga almost looks like he’s going to buy it, and then he snaps himself out of it. “Why did you kiss me?”

The word _kiss_ sounds the way a hand pressing on his breastbone feels, soft and insistent, nearly making him topple over.

Sento makes a face at him. “So you would be quiet.”

“So I— _what_.”

“See?” Sento pats Ryuga on the shoulder and pretends his hand isn’t shaking just a little. “It worked.”

.

When he wakes up in the bed, the lab empty except for him and Ryuga at his bedside, he nearly winces. Partly because he’s injured from the last fight and partly because this means there’s no one else to fill the silence, only Ryuga.

“You all right?” Ryuga asks, more slowly and softly than he’s been in a while, and this tone of voice only makes Sento feel the pressure of warm hands curling over his thighs, his arms, down his stomach. At a certain point, he has to wonder if this is less the synesthesia and more his own medicine-wrought fantasies.

“Yeah,” he says, the word coming out thick and raspy. “What happened?”

“Dislocated your shoulder,” Ryuga says, patting him on his very much in-place shoulder. The touch jolts him, interacting with his voice in the most unfairly intimate of ways. “We put it back, but the medicine Sawa brought knocked you out cold. Probably for the best.”

Sento rotates his shoulder, only wincing a little. “Thanks, I guess. Where are the girls?”

“Monitoring for more Hokuto troops.” Ryuga’s hand hasn’t moved from his shoulder, fingers just absently stroking his collarbone. Sento swallows. “Do you want me to call them?”

Sento honestly thinks he might die if Misora and Sawa had to see him like this. “No. What are you doing?”

“In general?” Ryuga frowns down at him. “I’m watching over you, obviously.”

Sento manages an eyeroll. “Unnecessary. You should be out there in case they need help.”

“I think if the Hokuto guys try anything against Sawa, _they’ll_ be the ones who need help,” Ryuga says, and the laughter in his voice sends the sensation of feathers tickling the back of Sento’s neck and behind his knees and under his arms. He tries not to squirm

“Do you not want me to be here?” Ryuga asks after a moment, removing his hand so the warmth is gone from Sento’s shoulder. “’Cause you can just say so.”

“Okay.” Sento struggles himself into a sitting position and says, “I don’t want you to be here.”

Ryuga looks genuinely hurt for a moment. “Why not?”

“Sometimes people just want to be alone, Banjou.”

Ryuga stares at him, disbelieving. “Is this about your voice thing?”

Sento falters. “My—my what thing?”

“You know.” Ryuga shrugs and waves one hand absently. “Misora said you had a voice thing. You don’t like certain ones or they sound different to you or something. And I’ve noticed you get weird sometimes when I speak like you want me to stop.”

“You notice things?” Sento asks before he can help himself, trying to ignore the sensation of hands warm on his back, sliding around his body. Ryuga shoots him a glare. “Okay, fine, you’re right. I don’t—I have this thing, where sounds translate to touch. And not all of them are nice.”

“Oh.” Ryuga nods, accepting this at face value. “So, like, my voice sounds like nails on a chalkboard or something?”

“No, it’s like where hearing nails on a chalkboard feels like someone is choking me,” Sento explains. His spine is loose like jelly, like someone has unhooked all the tension from it. “And your voice is… it’s different. It feels different.”

Ryuga leans closer. “Bad different?”

Maybe it’s the medicine or maybe it’s how he can see Ryuga’s eyelashes fluttering dark against his skin at this angle, but Sento can’t bring the lie from the tip of his tongue out into words. “No.”

Ryuga’s eyebrows shoot up. “No? It’s not bad?”

“Please just stop talking,” Sento sighs, closing his eyes and rocking his head backwards into the wall. Every minute he spends in this room feels like he’s coming unraveled, his hands and feet shaking, his throat feeling cold like someone has kissed it and then stepped away every time Ryuga stops speaking.

There’s silence for a minute, and then Ryuga asks, carefully, “Do you really want me to stop?”

Sento buries his head in his hands and groans. There’s no one else around, no one but him and Ryuga and the secret of his desire coming unlocked and pulled upon until everything in him is tangled up in the sound of Ryuga’s voice.

Ryuga’s hand touches his thigh, almost cautiously, barely there over his jeans, but still enough of a touch that Sento has to bite his lip.

“Don’t do this,” Sento warns. “Not unless—not unless you really—”

“Really want it?” Ryuga finishes when Sento can’t. He hates that, too, how well he can read him, how he’s a puzzle piece slotting against Sento’s jagged edges perfectly, how his voice catches the trail end of his thoughts and shines a light on them. “What if I do?”

Sento summons a baleful glare. “Don’t play with me, Banjou.”

“I’m not playing,” Ryuga insists, and his thumb digs in to the inside of his thigh, just a little. “Is it just my voice? Do you want me to just keep talking?”

He does, he _really_ does. The word ‘yes’ doesn’t come to his lips though, so he just jerks his head in a nod and closes his eyes so he doesn’t have to see whatever stupid expression is probably on Ryuga’s face.

“About anything? Okay,” Ryuga coughs, clears his throat, seems suddenly unable to find words. Sento’s leg twitches beneath his touch, and his palm flattens against it, holding him down. “How long has this been—a thing? Like, since you met me? Because I only noticed you kept telling me to shut up and go pump some iron whenever you got annoyed, but I figured you were just always annoyed.”

There’s goosebumps all down his arms and a dreadful, wonderful heat pooling in his belly. Sento exhales, opens his eyes just enough to see Ryuga watching him in clear fascination, a question that’s already been answered in his gaze.

“You _are_ annoying,” Sento mutters.

Ryuga laughs and his palm slides along the width of his leg and curls into the inside of his thigh. “So that’s a yes?” he teases, the sound of his voice flickering in scattered touches all over Sento’s body. “Has it ever… have you ever gotten off from it?”

The slight tremble of embarrassment in Ryuga’s voice does nothing to quash the sensations that come of it, the way he voices the question sending a dizzying spiral of heat down Sento’s spine until he’s shaking.

“No,” he manages to breathe. His jeans are so tight he wants to claw them off. “Not—not just your voice. Not yet.”

“How much more?” Ryuga leans over him, watching with keen eyes as Sento tries and fails to calm himself down enough to focus on the question, to find an answer somewhere in his mind that’s buried beneath the electrifying feeling of Ryuga’s voice so close to him and his hand trailing up his thigh.

“You’re not talking enough,” Sento complains, and the sound of Ryuga’s half-breathless laughter sends a flutter up his chest like someone has snaked a feather across his skin.

“Sorry, I didn’t know what the goal was.” Ryuga pauses, licking his lips, and Sento’s hands itch, both from his voice and from the overwhelming urge to shove Ryuga’s hands down his jeans. “Do you—do you get this with anyone else?”

“God, no.” Sento rolls his eyes, maybe a bit dramatically, but it’s the only avenue of control he has left. “If this happened with anyone else I would have to kill them.”

“You’re doing that thing where you’re joking but you sound serious so I don’t know how much you _are_ joking,” Ryuga says. “Do you want me to kiss you?”

“No.” Sento takes a shuddering breath, trying to soak up the feeling of warm hands pressing into his bare back, his shirt itching over his skin. “Just keep talking.”

“You want me to make you come with just my voice?” Ryuga’s tone is half-teasing, half-genuine, and something new flares in Sento’s stomach at the thought of what it promises. “I thought you needed some more help. What if—”

Instead of finishing his thought, he trails his hand higher up Sento’s thigh and wraps it gently around his growing erection, squeezing just once, a test. Sento jerks up into the touch, but even that is nothing compared to the feeling of fingers trailing up the backs of his legs and digging deep into his hips to leave ghost bruises. Ryuga’s hand is only in one place but it feels like he’s being touched all over, the heat of desire curling over his spine, crawling across his neck.

“Talk,” he says, his voice low and needy despite the command. “I need you to talk.”

“You, ah,” Ryuga hesitates, and his hand strokes up the length of Sento’s dick, careful and searching, but so, so warm. “You’re kind of an idiot, you know that? For someone so smart and all…”

Sento snorts. “You’re one to talk.”

He can hear Ryuga’s grin before it appears. “You would only do this because you don’t have the energy to hide it anymore, right? Or maybe it was the medicine, but I think I like you better when you’re honest. You spend a lot of time trying to hide yourself from everyone.”

“I did not ask for a psychoanalysis,” Sento says through gritted teeth, but every word out of Ryuga’s mouth hits him like nails scratching down his back—rough enough to hurt, but not unpleasant, not enough to bleed. Just enough to arch him off the bed, closer to Ryuga, his chest rising and falling until he is so, so near—

“I know, but I don’t think you would listen any other time,” says Ryuga, and when Sento looks at him, there’s a flush creeping down his neck, disappearing into his shirt. He wonders, briefly, how much of an effect seeing him like this has on Ryuga, and the next moment, all thoughts are melting out of his brain when Ryuga slides his hand down his jeans.

“I didn’t think…” Ryuga pauses, running his tongue over his lips. Sento is suddenly seized with the urge to kiss him again, but he doesn’t think he can quite manage it. “I didn’t think I’d ever want to do anything like this with anyone again, but you—you saved my life. Changed my life. Sento—”

Sento opens his mouth to say something, but what comes out instead is “Hmgmhhg” as Ryuga swipes his thumb across the head of his dick and then slides it upwards and Sento’s whole body feels like something has simultaneously clenched all his muscles and tugged all his tendons loose one by one.

“Say my name,” he whispers, curling his hand around Ryuga’s free one and pulling it to his chest. Ryuga obligingly presses his palm to Sento’s heart, no doubt feeling his triple-rate heartbeat and the heat of his chest. “Say it again.”

“Sento,” says Ryuga, like a finger tracing every knob of his spine up and down. “ _Sento_ ,” he says again, warmer and deeper, like lightning sparking under his skin. “I think—”

Whatever he thinks, Sento can’t hear it. The pressure splits apart inside him and he gasps, every inch of his body shivering from the friction as Ryuga’s hand between his thighs squeezes and his voice washes over him like a wave. The orgasm is heady and dizzying and makes him feel a little like he’s floating or maybe sinking and that would be enough, except Ryuga keeps speaking.

“I don’t know if now’s a good time, but I haven’t—haven’t stopping thinking about kissing you?” It’s phrased like a question, and when Sento opens his eyes slowly to look up at Ryuga’s face, the question is mirrored in his gaze. “I guess I should’ve started with that. I don’t even know if you remember, with all the shit that’s happened but—”

“I remember,” says Sento, and reaches up grab the collar of Ryuga’s jacket and pull him down onto the bed. “You can stop talking now.”

Ryuga grins, lopsided and warm. “I thought you liked me talking.” He lets Sento take both his hands and interlace his shivering fingers into Ryuga’s. “Or is that just when you need me to—”

“Shut up,” Sento says pointedly, and drags him in for a kiss. Ryuga breaks it just to laugh, a puff of air across Sento’s cheeks and whispered _You’re so easy_ that feels like fingers tap-dancing on his stomach and Sento takes a breath and kisses him again.

This time, he thinks, it’ll be easier. This time, he can feel all the touches for real.


End file.
